1. Field of the Invention
The present invention relates to a process for treating a surface of a semiconductor substrate, and more specifically, to a process for cleaning a surface of a semiconductor substrate prior to forming an epitaxial layer a CVD layer a thermal oxide layer, a thermal nitride layer, or other film layer on the substrate.
2. Description of the Related Art
In a known process for cleaning a surface of a semiconductor substrate, the surface is wet cleaned with an aqueous solution containing hydrogen peroxide and ammonia (for example, RCA Review, June 1970, pp 187-206). The cleaning efficiency of this process is, however, unsatisfactory.
A more effective process for cleaning a surface of a semiconductor substrate is known, in which the surface of the semiconductor substrate is preoxidized (also referred to as sacrifical oxidation) before wet cleaning as mentioned-above. This process comprises, for example, sequentially wet cleaning a substrate, oxidizing a surface of the substrate, removing the oxidized layer from the substrate, wet cleaning the surface of the substrate again, and forming a required layer on the surface of the substrate. However, this process is disadvantageous in that it involves many complicated steps, including the oxidation step. Moreover, the heat treatment necessary for oxidation causes contaminants to diffuse into the semiconductor substrate, so that removal of the contaminants is made more difficult. Particularly, when an extremely thin layer such as a gate insulating layer of a MOS-VLSI is formed on the cleaned surface of the substrate, such remaining contaminants cause a deterioration of the extremely thin layer.